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BIO210 - Brahmbhatt - Quiz 7 Incomplete Dominance
BIO210 - Brahmbhatt - Quiz 7 Incomplete Dominance
17
Biology
Undergraduate 2
10/22/2013

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Cards

Term
Define complete dominance and give an example.
Definition

The presence of the dominant allele masks the appearance of the recessive.

 

Thus, the phenotypes of the the heterozygote (Aa) and the dominant homozygote (AA) are indistinguishable.

 

Example: Mendel's peas

[image]

Term
Name five exceptions to Mendel's complete dominance.
Definition
  1. Incomplete Dominance
  2. Multiple Alleles
  3. Epistasis
  4. Pleiotropy
  5. Polygenic Inheritance
Term
Define incomplete dominance and give an example.
Definition

Neither allele is completely dominant, and the F1 hybrids have a phenotype somewhere between those of the two parental varieties.

 

Example: Snapdragons

[image]

Phenotypic Ratio: 1 red:2 pink:1 white

Term
Doesn't incomplete dominance provide evidence for the blending hypothesis of inheritance since red and white make pink?
Definition

NO! The blending theory implies that the original traits (red and white) could never be retrieved from the pink hybrids, which is incorrect.

 

The segregation of the red-flower and the white-flower alleles in the gametes produced for flower color are heritable factors that maintain their identity in the hybrids (as seen in the incomplete dominance card).

 

2 pinks produce the 1 RED:2 pink:1 WHITE ratio.

Term
Give an example of when there may be multiple alleles on the same gene (and when I say multiple I mean more than two).
Definition

Blood type. ABO blood groups in humans are determined by three alleles on a single gene.

 

There are four blood types (A, B, O, AB), but there are still three alleles (A, B, O).

Term
What's special about the alleles Iand IB that allows humans to have a blood type of AB?
Definition
They're codominant.
Term
Define codominance
Definition
Two alleles each affect the phenotype in separate, distinguishable ways.
Term
What blood type would you have if your genotype were homozygous recessive?
Definition

O

 

[image]

Term
What distinguishes one blood type from another?
Definition
Sugars present on the membrane (or lackthereof in the case of type O).
Term
Define epistasis and give an example.
Definition

Gene at one locus alters expression of gene at another locus

 

Example: The dogs!

The E/e gene is epistatic to the B/b gene. 

[image]

B=Black

b=brown

E=Expression of other gene at other locus

ee= Stops/halts expression

 

Notice all the ones with "ee" are albino. 

Term
Define pleiotropy and give an example.
Definition

One gene/many phenotypes

 

Pleiotropic alleles are responsible for the multiple symptoms associated with certain hereditary diseases, such as cystic fibrosis and sickle-cell disease.

 

 

Example: Hemoglobin and sickle cell disease

 

 

Term
Define polygenic inheritance and give an example.
Definition

This is the additive effect of two or more genes on a single phenotypic character, or one gene with multiple phenotypes. (Many genes/one phenotype)

 

Example: Skin tone

 

(Regarding skin tone, you can't say someone's skin tone is either _____ or _____; skin tone varies in gradations allong a continuum).

 

Also, A, B, and C genes in various genotypic combinations lead to different skin tones.

 

[image]

Term
Polygenic inheritance is the converse of _____________.
Definition

Pleiotropy.

 

(Since pleiotropy is one gene/multiple phenotypes and polygenic inheritance is many genes/one phenotype).

Term
What are epigenetic factors? Example?
Definition

Factors unrelated to inheritance.

 

The outcome of genotype lies within a phenotypic range that depends on the environment in which the genotype is expressed.

 

For example, hydrangea flowers of the same genetic variety range in color from blue-violet to pink, whith the sade and intensity of color depending on the acidity and aluminum content in the soil (so solely environmental stuff).

 

[image]

Term
What are pedigrees used for?
Definition

These are used for determining possible offspring based on family history. 

 

[image]

Usually goes eldest child to youngest child from left to right.

 

[image]

 

Term
Two methods of testing a fetus for genetic disorders?
Definition
  1. Amniocentisis
  2. Chorionic villus sampling (CVS)
Term

If HbA is a normal allele and Hbs is a Sickle cell/mutant allele, how many possible phenotypes are there?


What are they?


The number of phenotypes indicates that the gene for hemoglobin is ______________.

Definition

3.

 

HbAHbA - You're have normal hemoglobin

HbAHbS - You're a carrier for sickle cell anemia

HbSHbS - You have sickle cell anemia/mutant hemoglobin protein


Pleiotropic.

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